Magnetic switch



Oct. 23, 1956 E. E. GOODALE ETAL 2,768,312

MAGNETIC SWITCH 5 Sheets-Sheet 1 Filed Feb. 25, 1954 h m 9 42 m momwr Q eJ t t t flA e k r nL nu e H I h m T dn mu, ob R jw m l,

Oct. 23, 1956 Filed Feb. 25, l954 3 Sheets-Sheet 3 BIAS BIAS

Q Inventor's: g Edmund EGooda/e,

Roland M. Lichtenstein,

y /f ew Their- Attorney- United States Patent MAGNETIC SWITCH Edmund E. Goodale, Scotia, and Roland M. Lichtenstein,

Schenectady, N. Y., asignors to Generai Electric Company, a corporation of New York Application February 25, 1954, Serial No. 412,431 11 Claims. (Cl. 307-88) This invention relates to magnetic switches, and has special reference to a magnetic switch that is adapted for use as a sealer with computer apparatus.

In computer apparatus, it is often necessary to scale down or divide the number of a plurality of received indicating marks such as electric signal pulses so that the pulses can be more conveniently counted or otherwise employed by a register. For example, an electromechanical register is unable to count electric signal pulses at the high rate which may be involved in nucleonies counting applications. Therefore, when used in nucleonics counting operations, such a register is more satisfactorily operated through a sealer which provides one output pulse for a given number of input pulses. Such sealers employ a plurality of vacuum tubes arranged in a ring in such a way that only one tube can conduct and all of the others are cut off. An input pulse is then transferred as a conducting state from tube to tube around the ring. When the conducting state has traveled once around the ring, an output circuit responds, thus giving an output response at the rate of one for a given number of input pulses. Such a ring of vacuum tubes may also be considered as a switch which passes only one out of a number of pulses. Arrangements similar to the foregoing may also be employed for purposes other than for sealing, as for storing a particular pattern or number.

Vacuum tube sealer circuits of the type described above, however, possess certain disadvantages. The vacuum tubes consume power, even when there is no input, when they are merely storing the input pulses. Further, vacuum tubes have a rather limited life and frequently cause the sealers to fail in operation. In an attempt to overcome these disadvanages, magnetic switching elements have been used in equivalent circuits. These switching elements comprise magnetic cores having very distinct stable magnetic states depending upon the direction of magnetic saturation of the cores. These cores are arranged in a ring and operate in a manner very similar to that described above in connection with the ring of vacuum tubes. Heretofore, such magnetic switching arrangements have been feasible only when the magnetic material has had a nearly ideal magnetization curve; that is, a magnetization curve which was rectangular in configuration. A nearly rectangular magnetization curve was necessary in order that undesired changes in magnetic field strength not falsely operate the next succeeding switch in the ring. A material possessing such a desired magnetization curve is known as Deltamax. This material has been successfully used in a magnetic switch; however, eddy current losses limit the scaling speed of Deltamax, and the magnetic properties of this material can be altered by merely bending it, thus necessitating very delicate handling. Further, this material is relatively expensive. In overcoming these defects, the present invention was conceived.

It is therefore an object of this invention to provide an improved high speed magnetic switch.

It is a further object of the invention to provide a magnetic switch for use as a sealer capable of counting electrical signal pulses at a very high rate.

It is still another object of the invention to provide a high speed magnetic switch employing magnetic cores having a relatively high electrical resistivity to prevent the induction of eddy currents.

It is still another object of the invention to provide magnetic sealers employing low cost ferrite magnetic core materials.

In accordance with the invention, a number of ferrite cores, each respectively having an input, an output, and a pulse winding, are connected in a ring. The pulse windings of one set of alternate cores are connected in series electrical circuit relationship, and the pulse windings of the remaining set of alternate cores are also connected in series circuit relationship, with the two series circuits thus comprised being alternately connected to a source of electrical signal pulses to be counted through a suitable coupling circuit. Each of the cores thus connected is capable of retaining magnetization in either one of two directions, hereinafter referred to as the positive magnetic state and the negative magnetic state, and can be switched from one magnetic state to the other by application of a suitable switching potential supplied thereto by either the input or pulse windings. The input and output windings of all the cores are so interconnected that a reversal of the magnetic state in one core by an input pulse supplied to the pulse winding thereof, causes a reversal of the magnetization of the next succeeding core in the series. In this way, the magnetic state of successive cores can be serially switched to thereby cause a particular magnetic state to be transferred along throughout the series. To achieve his effect, the output winding of each core is connected to the input winding of the next succeeding core in the series through a respective rectifier and a voltage bias source. Each rectifier is connected in such polarity as to be normally blocked off by the bias voltage, the bias voltage being large enough so that only a large rate of change in magnetic flux will sufiice to overcome it and reverse the stable state of the succeeding core. Because of this construction, it is possible to use a ceramic ferrite core material which has low eddy currents, and is easily handled. This material can be used, despite the fact that the magnetization curve of the ferrite core material is not perfectly rectangular, for the small changes at the top and bottom of the curve of the preceding magnetic core have no effect upon the succeeding magnetic core due to the rectifier and bias battery. Provided that the ratio of the slope of the side of the curve to the slopes of the top and bottom of the curve (the quality factor) exceeds six, the magnetic switches of the invention will operate properly.

For a better understanding of the invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawings, like parts being indicated by like reference characters, wherein:

Fig. l is an enlarged view of a magnetic core and windings of a type suitable for use in apparatus embodying the invention;

Fig. 2 is a magnetization curve of the core shown in Fig. 1;

Fig. 3 is a circuit diagram of a magnetic sealer employing the magnetic cores of Fig. l and constructed in accordance with the invention; and

Fig. 4 is a circuit diagram of a coupling circuit suitable for use with the sealer of Fig. 3.

Referring now to Fig. 1, there is shown a toroidal core 1 made of ferrite and having windings 2, 3 and 4 there about. Winding 2 terminates in terminals AA and is the pulse winding. Winding 3 terminates in terminals B-B and is the output winding; and winding 4 terminates in terminals C-'C and is the input winding. A suitable ferrite material is MP l.ll8.made by theGeneralCeramic and Steatite Company, and a satisfactory core of this material has been used with an inner diameter of /8,

an outer diameter of and a thickness of:%.;". Wound.

about this core was an input winding having eight; turns, and pulse and output windings, each having thirty-two turns.

Referring now to Fig. 2, there is shown amagnetization curve for ferrite, the material of core 1. This curve moved, the flux density drops inthe direction of the a arrow from point 21 to point 22. Boint 22" represents the stable positive magnetic state ofcore; 1'. Whena magnetic field of opposite polarity is then appliedto the ferrite, the fiux density drops from point-22in the direction of the arrow down to point 23. Point 23 represents negative magnetic saturation. When the magnetic field is again removed, the flux density drops from point 23 to point 24 inthe direction of the arrow. Point 24 represents thestable negative magnetic state. When a positive magnetic field is again applied tothe ferrite core. the fiux density increases from point 24 to point 21 in the direction of the arrow, closing the magnetization curve. Thereafter, as negative or positive magnetic fields are applied and then removed, the flux density will vary frompoint. 21 to 22 to 23 to 24 and back to 21, never again going through point zero to point 21. From the foregoing, it will be apparent that points 22- and 24, respectively representing the positive and negative stable magnetic states, make the ferrite core suitable for use as a magnetic switch. The ratio of the slope of'the sides of the-magnetization curve to the slope of either the top orbottom of the curve is known as the quality factor of the material. It has been found that with the present invention, a core having a quality factor in excess of approximately six can be utilized in practice for a magnetic switch, thereby eliminating the prior art requirement for nearly perfectrectangular magnetization curve.

In Fig. 3 is shown a scaler using ferrite magnetic switches of the type shown in Fig. 1'. There are ten such ferrite cores, and they are shown as linear elements for convenience in drawing; however, each element represents the toridal' core shown in Fig. l. Assigning the cores consecutive numbers starting from 31, then the pulse windings 31A, 33A, etc., of the odd numbered cores cuitrelationship, and thepulse windings 32A, 34A ,ete, of the even-numbered cores 32, 3'4, etc., are also con; nectedinseries; The last two pulse windings. of both series of cores, windings 39A and 40A, are connected together ata point 42; which point is at groundpotential, and input terminals EE are respectively connected. to

theodd'and even-numbered sets of pulse windings. The output-wmdmgsof-each of'the cores are indicatedat 315 through 403, and the input windings are indicated. at

31C through 40C; The input windings 31C to 40C areso wound about their respective cores that any current therein will induce a change in the magnetic:stateof the coresso that the cores are magnetized in a state that is opposite in polarity to that induced by the associated pulsew-indings 31A to 40A. The output winding on each core is connected to the input winding of the next succeeding core inthe series as, for example, 31B is connected to 320), these connections forming the ring mentioned above, with the ring beingcompletedhy connecting outputwinding 40B; to input windingfilc. The out- 31, 33, etc., are connected in series electrical cir-.

put winding of each core is also connected through a respective germanium. rectifier 41 to the positive. terminal. of a battery 43, which battery has its negative terminal at ground potential. The battery 43 and rectifiers 41 are connected in opposition, in a manner such that current does not flow through the rectifiers until the bias supplied by the battery is overcome. One terminal of each input winding, except winding 31C, is also connected directly to ground potential. Winding 31C has one terminal connected to. ground, potential through a resistor 44 which serves as. an output load resistor, the output pulses to be counted appearing across resistor 4-4 at terminals D D In order-to supply electrical pulses of a given polarity and magnitude sufiicient; to operate the'magnetic switches, a coupling circuit receptive of pulses to be counted is connected to the odd and even-numbered pulse coil series, such a coupling circuit being depicted in Fig. 4. This circuit includes a pair of. blocking oscillators 45 and 46 which include respectively transformers 47' and 43; thetransformers serving to provide feedback between the anodes and the control grid-cathode circuits ofthe oscilla-tors. As can be seen from the drawing, these-tubes arenormally biasedto cutofi; by a bias potential applied to their control grids. The anode of tube 46 is con nected by a diode to a winding of transformer 47, the diode being so connectedthat only positive voltage pulses can'pass therethrough. The input to the first blocking oscillator 46 is applied across terminals F-F, and the oufputs from; both bit. osclliatcrs are taken from their cathodes and applied to-terminals EE, which lastnamedterminals correspond toterminals EE in Fig. 3, the circuits of- Figs. 3 and 4 being interconnected. When the circuit of Fig. 4- is connected to that of Fig. 3, the pulses from blocking oscillator 45 will be applied to the even-numbered series of pulse windings, while the output from blocking oscillator 46 will be applied to the odd-numbered series of pulse windings.

In explaining the operation of the circuits shown in Figs. 3 and 4, let it be assumed that core 31 is in its negative or downward stable magnetic state, while the remaining cores 32-49 are all'in their positive or upward magnetic states. Referring to Fig. 4, when a negative input pulse 49. is. applied between terminals F-F, blocking oscillator 46 will be triggered and will produce a positive pulse 49A which is applied to the odd-numbered series of'pulse windings. Since only core 31 is magnetized in a downward direction, all of the remaining cores being magnetized in the upward'direction, pulse 49A can only, eifect core 31 This pulse changes the directionof magnetization of core 31' from its negative stable magnetic state to its positive stable magnetic state. The ensuing large rate of change in flux density induces a voltage in output winding 3113 which is sufficient to overcome the;

P biaslsupplied by biasbattery 43 to rectifier 41, andresuits in theflow of current through input winding 32C of-core 3 2. The current in winding 32C then changes the stable magnetic state of core 32 from positive to negative, and'theremaining cores, including core 31, are allleft' in their upward or positive stable magnetic state. When the anode of blocking oscillator 46 swings positive,

apositive pulse is transmittedthrough diode 50 to trans-- former 47, which pulse serves to trigger blocking osci1-. lator 45 and producesa positive pulse 49B/at a time.sub sequent to the-,time thatpulse 49A appears. When this secondpulse 49B appears at its terminal E, the foregoing procedure is again repeated for the even-numbered cores, andcore 32 ,7which was in its negative or downward stable magnetic state, assumes its positive or upward stable magnetic state. In the process, a signal pulse is supplied to the input winding of core 33 so that core 33 assumes its negative or downward stable magnetic state. It will thus be, seen that input signal pulses have caused the negative stable magnetic state of core 31. to, be trans: mitted around. the ring of cores successively-to cores 32 and 33. Succeeding negative input pulses 49 appearing across input terminals F-F will continue this process until finally core 31 again assumes its original negative or downward stable magnetic state. This will occur after a total of five such input pulses have appeared so that after the fifth pulse, a potential will be developed across output resistor 44, which is connected to input coil 31C. This potential appears across output terminals D-D in the form of a series of positive pulses which can now be supplied to an electro-mechanical type of counter since they have only one-fifth the frequency of the input signal pulses.

It remains now to show, assuming again that core 31 is in its negative stable magnetic state and all of the other cores are in their positive stable magnetic states, that a positive pulse applied to lower input terminal E will eflfect only cores 31 and 32, causing core 31 to assume its positive stable magnetic state and core 32 to assume its negative stable magnetic state. Taking core 33 as an example, this positive pulse excites pulse winding 33A and thereby induces a voltage in output winding 33B which tends to drive a current through input Winding 34C of core 34. However, since core 33 is already in its positive stable magnetic state, its state of magnetization changes along the flat upper portion of the hysteresis loop in Fig. 2, the flux in this core changing so slowly that the voltage induced in winding 33B is too small to overcome the potential of bias battery 43, which means that no current can fiow in windings 33B or 34C. When the input pulse disappears, a current again arises in output winding 33B, which current tends to be opposite in direction to that previously induced in this winding by the input pulse, and is, consequently, blocked by rectifier 41 connected to winding 33B. Therefore, it will be seen that the positive input pulse only reinforces the positive state of the other odd-numbered cores and cannot effect any of the other even-numbered cores, only cores 31 and 32 being effected thereby.

Finally, it only remains to be shown that no current can flow between cores 31 and 40, and between 32 and 33, when core 31 assumes its positive and core 32 assumes its negative stable magnetic state. As core 32 is being magnetized negatively, a voltage is induced in winding 32B thereof, which voltage tends to drive a current through winding 33C of core 33. However, this current cannot flow since it is blocked by rectifier 41 connected to winding 32B. Further, as core 31 is being magnetized in a positive direction, a Voltage is induced in winding 31C thereof, which voltage tends to drive a current through winding 40B of core 49. However, this current cannot flow because the voltage induced in winding 31C is unable to overcome the blocking action of bias battery 43. There is only one other possibility for the interaction between cores 31 and 32 to elfect the other cores. As the input pulse is applied, there arises a secondary current in the interconnections between windings 31B and 32C, which current gradually increases in magnitude. When the input pulse has reached its maximum, the secondary current previously noted subsidies as it is gradually stopped by bias battery 43, and during this time interval the flux density in core 32 which has overshot point 24 and stopped at point 23 of Fig. 2 now returns to point 24. During this return, a voltage is induced in winding 32B of core 32 which tends to induce a current through winding 33C of core 33. However, the potential of the bias battery 43 is sufiicient to prevent such a current flow from occurring. It will, therefore, be clear from the foregoing that each successive pulse applied to terminals E-E of Fig. 3 sufiices only to reverse the polarity of the stable magnetic states of only two of the cores, the action in the circuit being isolated to these cores.

It should be emphasized that although the circuit of Fig. 3 has been used in connection with the coupling circuit of Fig. 4 to produce one output pulse for every five input pulses, other types of input circuits could be used.

For example, a bi-stable multivibrator could be used to produce only one output pulse for every input pulse applied thereto, alternate output pulses of this multivibrator triggering a blocking oscillator going to one set of pulse windings, and the other output pulses triggering another blocking oscillator going to the other set of pulse windings, blocking oscillators such as those shown in Fig. 4 being suitable for this purpose. Such an input circuit would enable the circuit of Fig. 3 to produce one output pulse for every ten pulses applied to the multivibrator, causing it to have a scale of ten.

It is believed apparent that if it is desired to use any number of cores in any type of magnetic memory device, this can easily be done by adapting the circuit of Fig. 3. For example, depending upon whether the input circuit produces one or two output pulses for every pulse applied thereto, a ring of two or four cores could be used where it is desired to have only one output pulse for every two pulses applied to the input circuit; or 20 to 40 such cores could be connected to form a ring which will give an output pulse for every twenty pulses applied to the input circuit. Moreover, if it is desired to know which core at any given time is in its negative stable magnetic state, the output winding of every second core may be disconnected from the next core in the ring and connected to the input winding of the preceding core, thereby forming a plurality of two core ring sets, and a neon bulb may then be placed across the output winding of one core in each set. Now when double pulses are fed into the pulse windings, only the neon bulb in the pulse pair including the core in its negative stable magnetic state will flash to indicate this fact.

While there has been described what is at present considered a preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made wherein without departing from the invention, and it is aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

l. A magnetic switch comprising first and second magnetic cores each being capable of having positive and negative stable magnetic states, said first magnetic core being in its positive stable magnetic state and said second core being in its negative stable magnetic state, bias means so intercoupling said first and second magnetic cores that a reversal in the magnetic state polarity of one magnetic core reverses the magnetic state polarity of the other core but any lesser change in magnetic state of one core will not affect the other, said bias means including a source of bias potential connected to said first and second magnetic cores and first and second rectifier means each connected to a respective one of said first and second magnetic cores and in series with said source of bias potential, said source of bias potential being connected to said rectifier means in such a manner as to oppose the flow of any current therethrough, and means for applying electrical pulses of a given polarity and magnitude alternately to said first and second cores for alternately reversing the magnetic state polarity of said cores.

2. A magnetic switch according to claim 1, wherein the material of said first and second magnetic cores is a ferrite and has a quality factor of at least six.

3. A magnetic switch comprising a plurality of magnetic cores each being capable of having positive and negative stable magnetic states, one of said magnetic cores being in a stable magnetic state of given polarity and each of the remaining cores being in a stable magnetic state opposite in polarity to the given magnetic state polarity of said one core, each of said magnetic cores respectively having an input winding, an output Winding, and a pulse Winding, the pulse windings of one set of alternate cores being connected in series and the pulse windings of the other set of alternate cores also being c nnectcdinccricsme .cutput nd g c ca ht r u so coupled tothe inputwinding of the next corev that. the;cores forma closed ring iniwhicha currentinducedf in anyoutput. coil. due toa' change in magnetic statcPQ: larity. of its associated corewill tend'tocause a reversal in; the magnetic state polarity of the next core. in the ring, bias means connected. between the input and output coils of. said magnetic cores for biasing said cores so that only a complete reversal of magnetic state polarity of, onecore willreverse-v the magnetic state polarity of the next core in the ring, and means for applying electrical pulses of a given polarity. andmagnitude alternately. to the two respective sets of. series-connected pulse windings for reversing, the stable magnetic state polarity oi anycore having said; given polarity.

I 4. Amagnetic switch according to claim3, wherein the magnetic material of. said magnetic cores is a ferrite and has .a quality factor of at leastsix,

5. Av magnetic switch according to claim 3, wherein said bias means includesa-source of, biaspotential and a plurality of rectifier means connected thereto in such a manner that saidsource of bias-potential, opposes the flow of any current through said rectifier means, said source of bias potential being connected to the input coils of each of said magnetic cores and each respective one of saidplurality of rectifier means being'connected toan outputwinding of a respectiveone of said plurality. of magnetic cores.

6. A. magnetic switch accordingto, claim 5, further including load means connected-to the input coil of said one magnetic core for providing; an output pulse whenever this core changes the polarity, of its stable magnetic state;

7. A magnetic switch according-to claim 6', wherein the magnetic material of said magnetic cores is a ferrite and has a qualityfactor of atleast six.

8.. A magnetic switch sealer comprising N magnetic coreseach beingcapable of having positive and negative stable magnetic states, N beingthe number that, is twice. the scale-factorby which it is-desiredto reducethe number of input pulses, one of saidmagnetic cores being in its negative stable magnetic state and eachfof the-remaining coresbeing in its positive stable magnetic state, said cores being made of a magnetic material having a hysteresis loop with aquality factor of at least'six, each 4 of'saidmagneticcores respectively having an input winding, an output winding, and' apulse winding, the pulse windingsof'one set of alternate cores being connected in seriesand the pulse windings of the other set of alternate next corein the ring, a,source-, of: bias potential andNf rectifier means connected thereto in such a manner that:- said source of' bias, potentialopposes the, flow of; any.

currentthrongh. saidv rectifier. means,..s aid. source of bias.

potential being connected, to the input coilsof each. of

said magnetic cores and each respective one of. said'N. rectifier meansbeing connected, to an output winding of; a

respective, one. of: said. N,magnet1c cores, said source: o'r? bias: potential being. suflicient. to so bias said cores that.

only a completereversaliofi magnetic-;statepolarity of one core will reversethe magnetic statepolarity of, the, next core in the ring,.and means receptive: of. saidzinput, pulses for-applying a pair ofelectrical pulses of. positive polarity. and given magnitude alternately to therespective: sets of series-connected pulse windings for changingthe negativestablemagnetic state polarityof. any. coreto: itspositive stable magnetic, state.

9"; A, magnetic switch sealer according to claim 8, Wherein the, magnetic material. ofgsaid magnetic cores is aierrite.

10. Amagnetieswitchsealer accordingto claim:9,,= furr ther including load-means connectedto the inputcoil of said. one magneticv core forproviding an output pulse whenever. this core changesthe polarity of its: stable magneticstate.

11. A magnetic, switch. sealer according toclaim; 10,. wherein said means, for applying electrical pulses comprises aipair of seriesconnected blocking oscillator means for Y producingapair of, output pulses ion eachinput pulseoap pliedtooneef saidcscillator means, the first, one of-saidpair. of output pulsesbeing. applied to-the-set of SIlS-CO11-?-- nected pulse windingstwhich includes thepulse- Winding of the core initiallyin its negative stablemagnetic state, and, the second one of, said pair of outputpulsesbeing; applied to the:other set of said pulse windings.

Referencesfiited in the file of this patent UNITED; STATES PATENTS 2,640,164- Giel etal, May 26, 1953' 2,666,151 Rajehman'et al. Ian. 12, 1954' 2,680,819 Booth- June 8, 1954, 

